The present invention relates to decorative sheet materials generally, and more particularly to the manufacture of decorative sheet materials suitable for use as a flexible weatherable paint film.
Manufacturers have shown increasing interest in using paint films in lieu of spray painting for providing a decorative surface finish for parts, such as automobile body parts. This manufacturing technique reduces the environmental concerns associated with painting and has the potential to reduce manufacturing costs. An automobile body part utilizing a plastic paint film to produce a high quality base coat/clear coat automotive finish is disclosed, for example, in U.S. Pat. No. 4,810,540, which is incorporated by reference herein. In producing the part, the paint film is typically formed into a contoured three-dimensional configuration corresponding to the shape of the outer surface of the part by suitable methods, such as by thermoforming.
Automotive manufacturers, for example, require that automotive parts have an exterior paint appearance which meets demanding performance and appearance specifications, such as weatherablility, resistance to ultraviolet light degradation, high gloss, and high distinctness-of-image (DOI). To meet these demanding requirements, paint film materials have been developed that have a number of layers of differing compositions and differing functions. For example, the paint films include a pigmented color coat layer, and where the paint film is intended to simulate the appearance of a base coat/clear coat paint finish, the film will also have an outer clear coat layer. In addition, the film may include a primer layer adhered to the color coat layer and an underlying adhesive layer as well as a thermoformable backing. The film may also have a removable protective mask layer which overlies and protects the paint film, and which can be removed after the automotive part has been manufactured.
Producing complex multilayer films of this type by conventional coating techniques requires multiple coating operations, typically performed by successive passes through a coating apparatus. The handling associated with each coating pass adds to the cost of the product and increases the opportunity for introducing flaws or defects which would result in inferior quality film materials.
The present invention addresses the problems and limitations associated with conventional coating technology and provides a process and apparatus for producing complex multilayer films with enhanced efficiency and assurance of quality. The method and apparatus of the present invention also provides the flexibility for producing various product designs or configurations.
In accordance with the present invention, multiple coating operations are performed in a single pass through the coating apparatus. The coatings are applied xe2x80x9cwet-on-wetxe2x80x9d as the film product is advanced through the coating apparatus. By this approach, complex multi-layer film products can be produced in a minimum number of successive passes through the coating apparatus. Multilayer films can be produced efficiently, economically and with a high assurance of quality. By reducing the number of passes required through a high temperature drying oven, product degradation is reduced. Additionally, the kinds of coatings which can be applied is expanded, making it possible, for example to apply temperature sensitive coatings or coatings of a viscosity or thickness which cannot readily be coated separately. The complex multi-layer film products can provide functional advantages that a single layer coating cannot provide.
In accordance with one broad aspect, the present invention provides a method of making a decorative sheet material comprising: directing a flexible carrier film through a coating station; depositing onto the surface of the carrier film a first coating layer of a solvent based clear coat composition; depositing onto the first coating layer a second coating layer of a solvent based pigmented color coat composition; directing the thus coated carrier film from said coating station through a drying station and drying said first and second coating layers; directing the thus coated and dried carrier film through a coating station; depositing onto the surface of the dried second coating layer a third coating layer of a solvent based primer composition; depositing onto the third coating layer a fourth coating layer of a solvent based adhesive composition; and directing the thus coated film from said coating station through a drying station and drying said third and fourth coating layers. Preferably, the first two depositing steps are performed during a first pass through said coating station, and the second two depositing steps are performed during a second pass through the same coating station.
In one embodiment the depositing steps are carried out by directing the carrier film past first and second successively arranged coaters which are mounted adjacent a cylindrical coating roll. The carrier film is guided onto the coating roll and the roll is rotated to advance the film while on the coating roll successively past the first and second coaters for depositing the first and second coating layers. In one preferred embodiment, the first and second coaters comprise respective slot coating dies mounted at spaced locations along the circumference of the coating roll. In another preferred embodiment, the first and second coaters comprise a multi-slot coating die mounted adjacent the coating roll.
The present invention also provides an apparatus for making a decorative sheet material comprising: a coating station having first and second coaters; means for supplying to the first coater of said coating station a solvent based clear coat composition; means for supplying to the second coater of the coating station a solvent based pigmented color coat composition; an unwind stand for receiving a roll of flexible carrier film; means for directing the flexible carrier film from the unwind stand through the coating station and successively past the first and second coaters for forming a first coating layer of clear coat composition on the surface of said carrier film and a second coating layer of pigmented color coat composition on the first coating layer; a drying station positioned adjacent the coating station to receive the thus coated film from the coating station and to dry said first and second coating layers; and a windup stand positioned for receiving the coated and dried film from the dryer and for winding the same into a roll. In one embodiment, the coating station includes a rotatably mounted cylindrical coating roll mounted for receiving the carrier film, and wherein first and second coaters are mounted adjacent said coating roll and successively arranged so that rotation of the coating roll advances the carrier film while on the coating roll successively past the first and second coaters for depositing the first and second coating layers.